The Complement Fixation Test (CFT) is a classical serological method for the detection of antibodies against pathogens of infectious diseases and has proved itself as a standard diagnostic method in many medical laboratories. With SERION CFT reagents, Institut VirionSerion GmbH offers a great variety of antigens that are important in infectious serology of bacteria, viruses and parasites. The complement fixation test performance is a micromethod according to the KOLMER technique and to DIN 58 969 as well as to the WHO guidelines. Complement fixation tests can be used as screening tests for acute infections. The fact that one IgM molecule is capable of activating one C1-molecule of the complement complex whereas 168 IgG molecules are necessary to achieve the same effect, emphasizes the significance of the test for the recognition of early infections. Positive CFT titres are often an indication for the presence of IgM antibodies or very high IgG antibody titres and are therefore an expression for an acute or recent infection, respectively. The CFT is especially helpful for acute respiratory infections: The, in general, strong IgG booster reaction is very well represented whereas residual titres of past infections are blanked out. Thedistinction between IgG and IgM antibodies is not possible. For research use only, not for use in diagnostic procedures.